/ Dictionary / Index D drop valve: Meaning and Definition of Find definitions for: drop' valve" Pronunciation: [key] a valve, as for a steam engine, that drops freely to close. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. drop the handkerchief drop window Related Content Daily Word Quiz: philtrum Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language